Abstract:

Calocedrus macrolepis is an ancient relict plant,and it is called an important ‘living fossil’ that lived in quaternary glacial epoch. Nowadays the species is one of second-class protected rare and endangered plants in China,and distributes in dispersal state and rarely gathers in a small cluster. Knowledge about characters of population and individual growth state of C. macrolepis is very useful for us to understand its living state and population characters, so as to protect and use it better. In this paper, individual growth state, interspecific competition and population structure in different canopy densities of C. macrolepis forests in the plateau area of central Yunnan Province were comparatively studied based on plot investigation. The results showed that: 1) there was an obviously exponential functional relationship between basal area at breast height and tree height, and there was an apparent turning point in the growth when DBH and tree height were 31－40 cm and 19 m respectively. Before the point, tree height grows more fast than DBH, and after the point DBH increased rapidly, and tree height growth slowed down till stopped. 2) In the central Yunnan province, natural forest land fragmentation of C. macrolepis was very common, and diameter class structure was very irregular and incomplete. 3) In the dispersal natural C. macrolepis forests, plant density and size were very different, which led to different average individual competition indexes in different forest lands. The smaller trees, the stronger the interspecific competition pressure. There was an apparent turning point when DBH was 31－40 cm. When the DBH was smaller than the point, the competition pressure was high, but sharply dropped with DBH’ increase; When the DBH was greater than the point, the competition pressure was low, and the change of competition pressure with DBH’ increase was very small. Therefore, it is very useful to expand its distributing areas by strengthening the administration of the forest edges and the forest gaps where there is small competition pressure. At the same time, according to the growth of natural trees, some suitable measures would be done during the management of man-made forests.

Key words: rare and endangered plant, Calocedrus macrolepis, competition, seedling regeneration